Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing the same.
Description of the Background Art
Photolithography is used to form a pattern. In the photolithography, a photoresist is applied onto a film to be processed and thereafter patterned by exposure to light and development. The film to be processed is patterned by performing etching or the like thereon using the patterned photoresist as a mask. Thereafter, the photoresist is removed.
A technique of partially changing the sensitivity of a photoresist used for photolithography is disclosed, for example, in Japanese Patent Laying-Open No. 11-186137.
In this publication, the film thickness of the photoresist at a bottom part of a level difference is selected such that the photoresist has a minimum or minimal sensitivity. This can prevent deterioration in the shape of the photoresist due to halation, according to the above publication.
However, when a film to be processed has a large level difference and a photoresist on the level difference is removed during patterning of the photoresist, a residue of the photoresist is produced at a corner portion of a lower part of the level difference. When the residue of the photoresist is produced, the residue of the photoresist functions as a mask, and the film to be processed directly below the residue of the photoresist cannot be removed by etching or the like. Therefore, it is necessary to remove such a residue of the photoresist.
However, addition of the step of removing the residue of the photoresist increases the number of manufacturing steps. Further, removal of the residue of the photoresist may cause damage to a base layer or adhesion of particles to the base layer. Furthermore, there may be a case where the residue of the photoresist cannot be completely removed.